> ## Documentation Index
> Fetch the complete documentation index at: https://easyaf.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# IApplicationBuilder

> Extension methods for IApplicationBuilder from Microsoft.AspNetCore.Http.Abstractions

## Definition

**Assembly:** Microsoft.AspNetCore.Http.Abstractions.dll

**Namespace:** Microsoft.AspNetCore.Builder

## Syntax

```csharp theme={"dark"}
Microsoft.AspNetCore.Builder.IApplicationBuilder
```

## Summary

This type is defined in Microsoft.AspNetCore.Http.Abstractions.

## Remarks

See [Microsoft documentation](https://learn.microsoft.com/dotnet/api/microsoft.aspnetcore.builder.iapplicationbuilder) for more information about the rest of the API.

## Methods

### <Icon icon="puzzle-piece" iconType="duotone" color="#419AC5" size={24} className="mr-2" /> UseCrossOriginIsolation <Badge color="green">Extension</Badge>

<Note>Extension method from `Microsoft.AspNetCore.Builder.ApplicationBuilderExtensions`</Note>

Adds Cross-Origin Isolation middleware to the application pipeline.
This enables SharedArrayBuffer and high-resolution timers required by WASM libraries.

#### Syntax

```csharp theme={"dark"}
public static Microsoft.AspNetCore.Builder.IApplicationBuilder UseCrossOriginIsolation(Microsoft.AspNetCore.Builder.IApplicationBuilder app)
```

#### Parameters

| Name  | Type                                               | Description              |
| ----- | -------------------------------------------------- | ------------------------ |
| `app` | `Microsoft.AspNetCore.Builder.IApplicationBuilder` | The application builder. |

#### Returns

Type: `Microsoft.AspNetCore.Builder.IApplicationBuilder`
The application builder for chaining.

#### Examples

```csharp theme={"dark"}
// In Program.cs
var app = builder.Build();
app.UseCrossOriginIsolation();
```

#### Remarks

This middleware adds the following headers to responses:

* `Cross-Origin-Opener-Policy: same-origin`
* `Cross-Origin-Embedder-Policy: require-corp`
* `Cross-Origin-Resource-Policy: same-origin`

  \<strong>Warning:\</strong> This may break third-party scripts and iframes.
  Use [CrossOriginIsolationOptions})](https://learn.microsoft.com/dotnet/api/microsoft.aspnetcore.builder.applicationbuilderextensions.usecrossoriginisolation\(microsoft.aspnetcore.builder.iapplicationbuilder,system.action\{cloudnimble.blazoressentials.server.middleware.crossoriginisolationoptions}\))
  to configure exclusions.

### <Icon icon="puzzle-piece" iconType="duotone" color="#419AC5" size={24} className="mr-2" /> UseCrossOriginIsolation <Badge color="green">Extension</Badge>

<Note>Extension method from `Microsoft.AspNetCore.Builder.ApplicationBuilderExtensions`</Note>

Adds Cross-Origin Isolation middleware to the application pipeline with custom options.

#### Syntax

```csharp theme={"dark"}
public static Microsoft.AspNetCore.Builder.IApplicationBuilder UseCrossOriginIsolation(Microsoft.AspNetCore.Builder.IApplicationBuilder app, System.Action<CloudNimble.BlazorEssentials.Server.Middleware.CrossOriginIsolationOptions> configureOptions)
```

#### Parameters

| Name               | Type                                                                                        | Description                                 |
| ------------------ | ------------------------------------------------------------------------------------------- | ------------------------------------------- |
| `app`              | `Microsoft.AspNetCore.Builder.IApplicationBuilder`                                          | The application builder.                    |
| `configureOptions` | `System.Action<CloudNimble.BlazorEssentials.Server.Middleware.CrossOriginIsolationOptions>` | Action to configure the middleware options. |

#### Returns

Type: `Microsoft.AspNetCore.Builder.IApplicationBuilder`
The application builder for chaining.

#### Examples

```csharp theme={"dark"}
// In Program.cs
var app = builder.Build();
app.UseCrossOriginIsolation(options =&gt;
{
    // Use credentialless instead of require-corp for less strict isolation
    options.CoepPolicy = "credentialless";

    // Exclude API paths from cross-origin isolation
    options.ExcludePaths.Add("/api/");

    // Exclude external resource paths
    options.ExcludePaths.Add("/external/");
});
```

### <Icon icon="puzzle-piece" iconType="duotone" color="#419AC5" size={24} className="mr-2" /> UseCrossOriginIsolation <Badge color="green">Extension</Badge>

<Note>Extension method from `Microsoft.AspNetCore.Builder.ApplicationBuilderExtensions`</Note>

Adds Cross-Origin Isolation middleware to the application pipeline with the specified options.

#### Syntax

```csharp theme={"dark"}
public static Microsoft.AspNetCore.Builder.IApplicationBuilder UseCrossOriginIsolation(Microsoft.AspNetCore.Builder.IApplicationBuilder app, CloudNimble.BlazorEssentials.Server.Middleware.CrossOriginIsolationOptions options)
```

#### Parameters

| Name      | Type                                                                         | Description              |
| --------- | ---------------------------------------------------------------------------- | ------------------------ |
| `app`     | `Microsoft.AspNetCore.Builder.IApplicationBuilder`                           | The application builder. |
| `options` | `CloudNimble.BlazorEssentials.Server.Middleware.CrossOriginIsolationOptions` | The middleware options.  |

#### Returns

Type: `Microsoft.AspNetCore.Builder.IApplicationBuilder`
The application builder for chaining.